Japanese Patent Application Publication No. 2005-221315, corresponding to U.S. Patent Application Publication No. 7121144 for instance, discloses a pressure sensor, a configuration of which is described as follows. A sensing member for sensing pressure is disposed on one end of a resin case which is combined with a housing unit made of metal. The housing unit includes a pressure medium introduction hole. The pressure medium introduction hole is used for introducing a pressure medium. The configuration of the pressure sensor causes the sensing member to detect a pressure of the pressure medium introduced through the pressure medium introduction hole.
A pressure sensor like the above-described pressure sensor is configured so that the pressure sensor is mounted to an installation block. The installation block is attached to a part of a pipe in which a cooling medium flows. FIGS. 11A and 11B illustrate a pressure sensor according to a related art, the pressure sensor being attachable to an installation block. A pressure sensor R1 according to the related art includes a case R10 made of resin and a housing unit made of metal. The housing unit includes a screw member R80 and a nut member R81. The pressure sensor R1 is mounted to an installation block R100 via an O ring R90 by screw fixation. The installation block R100 has a first connection member R51 and a second connection member R52. The first and second connection members R51, R52 are to be coupled with a pipe in which a cooling medium flows. The installation block further has a passage through which the first connection member R51 is communicated with the second connection member R52. In addition to the pressure sensor R1, a sight glass R60 and a charging valve R70 are to be mounted to the installation block R100 via the O-ring R90.
As described above: the installation block R100 is attached to a part of a pipe; the pressure sensor R1 having the case R10 is mounted to the installation block R100; and the case R10 is combined with the housing unit. In this case, there arises a problem that the number of parts and the number of man-hour requirement are large.